Composition Analysis and Antimicrobial Efficacy of Garlic Essential Oils in Varied Water-Based Delivery Systems: Insights into Organic Solvent, Emulsification, and Self-Microemulsification -

Composition Analysis and Antimicrobial Efficacy of Garlic Essential Oils in Varied Water-Based Delivery Systems: Insights into Organic Solvent, Emulsification, and Self-Microemulsification

Garlic (Allium sativum), native to central Asia, is known for its antimicrobial properties attributed to compounds like alliin. Garlic essential oil (GEO) is utilized in the food industry for its natural antimicrobial, flavoring, and antioxidant characteristics. GEO, obtained through steam or water distillation, contains diallyl sulfide derivatives, contributing to its antimicrobial activity. The antimicrobial efficacy of GEO depends on its chemical composition, influenced by garlic cultivar and geographical origin. While in vitro testing typically uses organic solvents, the challenge lies in formulating water-based systems for real food applications due to the poor water solubility of most essential oils (EOs). GEO has been formulated in water-based microemulsions and solid lipid nanoparticles, but the impact of food-compatible surfactants on its antimicrobial activity in emulsions remains unexplored. This study aims to investigate the chemical composition of GEO from different garlic cultivars and assess its antimicrobial activity in traditional organic solvents and water-based systems, specifically emulsions and microemulsions, shedding light on the influence of particle size on antimicrobial efficacy.

 Materials and Methods:

Two garlic cultivars: white-skin and purple-skin garlic bulbs

Non-ionic surfactants: Tween 80 and Kolliphor RH 40

Solvents: Propylene glycol and isopropanol

 Microorganisms:

Aspergillus flavus 335

Listeria monocytogenes 598

Escherichia coli 0157: H7

Staphylococcus aureus

Aspergillus niger

Salmonella typhimurium

 Methods:

 Isolation of Garlic Essential Oils (GEOs)

Hydrodistillation of crushed garlic bulbs from white-skin and purple-skin cultivars

Essential oils collected and stored for further use

Chemical Analysis of GEOs:

Gas chromatography coupled with mass spectrometry and flame ionization detector

Identification of chemical composition of  WGO and PGO

Formulation of GEOs in Different Delivery Systems

Formulation in Organic Solvent

Preparation of stock solutions of WGO and PGO in isopropanol

Dilution of stock solutions for antimicrobial activity evaluation

Formulation in Water-Based Emulsifying System:

Preparation of pre-concentrate with corn oil and surfactant

Emulsification of pre-concentrate to form WGO and PGO emulsions

Dilution of emulsions for antimicrobial activity evaluation

Formulation in Water-Based Self-Microemulsifying System:

Preparation of pre-concentrate with surfactant and co-surfactant

Formation of WGO and PGO  microemulsions

Dilution of microemulsions for antimicrobial activity evaluation

Particle Size Analysis of GEOs Emulsions:

Measurement of size distribution using static light scattering instrument

Particle Size Analysis of GEOs Microemulsions:

Measurement of hydrodynamic diameter using dynamic light scattering instrument

 Microbiological Evaluation:

Preparation of the Inoculums

Growth of microorganisms in suitable media

Antimicrobial Evaluation:

Agar well diffusion method for evaluating antimicrobial activity

Incubation  of plates and measurement of inhibition zones.

Result and Summary:

In this study, the antimicrobial activity of garlic essential oils (GEOs) extracted from white-skin (WGO) and purple-skin (PGO) garlic cultivars was investigated. WGO exhibited higher antimicrobial activity against tested microorganisms compared to PGO, likely attributed to its elevated content of total trisulfide derivatives.

However, the antimicrobial efficacy of both WGO and PGO was compromised when formulated in water-based delivery systems, such as emulsion and microemulsion, as opposed to isopropanol. The reduction in antimicrobial activity was particularly evident in emulsions, highlighting the impact of formulation on the effectiveness of GEOs.

Interestingly, the study revealed that decreasing the particle size of GEOs in water-based systems, specifically in microemulsions, enhanced antimicrobial activity compared to emulsions at equivalent concentrations. This finding suggests a potential avenue for optimizing the delivery system to harness the antimicrobial properties of GEOs in food products.

The results also underscore the need for careful consideration when choosing a delivery system for natural flavoring and preservative agents like GEOs in practical food applications. While organic solvents, such as isopropanol, demonstrated antimicrobial efficacy, the study proposes microemulsions as a promising alternative. However, further investigations are planned to explore the efficiency of microemulsions after dilution in food matrices, aiming to reduce surfactant concentration.

Moreover, the chemical composition analysis of GEOs revealed variations between WGO and PGO, with WGO exhibiting lower percentages of major constituents like diallyl trisulfide and diallyl disulfide compared to PGO. This insight into the distinct compositions of GEOs from different cultivars contributes valuable information for future applications.

In summary, the study provides insights into the antimicrobial activity of GEOs under various formulations, shedding light on the potential of microemulsions as a water-based delivery system. These findings contribute to the ongoing exploration of effective and food-compatible methods for delivering natural antimicrobial agents in the food preservation industry.

Reference:

EL-SAYED, H.S., CHIZZOLA, R., RAMADAN, A.A. AND EDRIS, A.E., 2017. Chemical composition and antimicrobial activity of garlic essential oils evaluated in organic solvent, emulsifying, and self-microemulsifying water based delivery systems. Food chemistry, 221, pp.196-204.